There are a variety of processes and equipment used for molding polymeric materials into molded articles. Injection molding is one type of process widely used to mold many different types of polymeric articles. There are two basic types of injection molding techniques. One type of injection molding technology uses a cold runner system 10, for example, like that shown in FIGS. 1A and 1B. Typically, the cold runner injection molding system 10 relies on a reciprocating screw extruder (not shown) to supply a molten polymeric material into a mold 11 via a nozzle 12 in fluid communication with the mold 11 through a nozzle seat 13. The mold 11 has a first mold half 14 and second mold half 15 that define a mold cavity that includes a sprue passage 16 formed through the first mold half 14, which directs molten polymeric material supplied from the nozzle 12 into a body cavity 17 forming part of the mold cavity. The body cavity 17 includes a runner passage 18 that directs molten polymeric material from the sprue 16 to two part cavities 19 and 20 through separate gate openings 21 and 22, respectively. The gates 21 and 22 determine the flow field of the molten polymeric material injected into the corresponding part cavities 19 and 20. After the molten polymeric material filling the sprue 16 and body cavity 17 has solidified, the mold halves 14 and 15 are separated and the solidified article removed. To facilitate removal of the molded article, a plurality of ejection pins 23 are mounted in the second mold half 15, and used, so as to push the molded article out of the second half 15.
Another type of injection molding technology uses a hot runner molding system. A hot runner injection molding system is similar in construction to a cold runner system except that the sprue and runner cavities are heated so that the molten polymeric material remains molten as it passes through to the part cavities. Thus, in a hot runner system, the molten polymeric material injected into the part cavities is typically the only molten polymeric material solidified and eventually removed from the mold.
Such conventional injection and other molding systems have been used to form a variety of molded articles having a wide range of feature designs and sizes. A variety of different polymeric materials have also been used to mold into articles using such equipment. One polymeric material known to be used in making injection molded articles is thermotropic liquid crystalline polymers (TLCP). On the molecular level, TLCPs are comprised of rigid moieties that form segments in the polymer chains. These rigid moieties are known as “mesogens.” TLCPs are known for exhibiting desirable properties, which can include one or more of high impact resistance, low coefficient of thermal expansion, resistance to chemical degradation, low weight, high strength, and high modulus among other properties.
There are limits to the mold feature designs and sizes that can be filled with known polymeric molding materials using conventional molding systems. Therefore, there is a continuing need for molding systems, especially injection molding systems, that are capable of molding articles having even smaller and more intricate design features. The present invention fulfills this need.